// Copyright 2017-2019 Lei Ni (nilei81@gmail.com)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package random

const (
	oneMillion uint64 = 100 * 10000
)

// Probability is used to represent a random probability.
type Probability struct {
	p uint64
	r uint64
}

// NewProbability returns a new Probability instance, the probability is
// is expressed a outOfMillion / one million, e.g. NewProbability(1) means
// there is 1 out of 1 million chance.
func NewProbability(outOfMillion uint64) *Probability {
	return &Probability{
		p: outOfMillion,
		r: LockGuardedRand.Uint64() % oneMillion,
	}
}

// Hit returns a boolean value indicating whether the random event is within
// the specified random range.
func (p *Probability) Hit() bool {
	return p.p > p.r
}

// Missed returns a boolean value indicating whether the random event is not
// within the specified random range.
func (p *Probability) Missed() bool {
	return !p.Hit()
}
